The invention relates to a rotary regenerative heat exchanger of the kind including a rotatable disc-like matrix through which the fluids between which heat is to be exchanged will flow between the end faces of the matrix.
In such a heat exchanger, seals are arranged to engage the end faces of the matrix to define separate portions in each of the end faces through which the respective fluids will flow. It is essential to keep the fluid streams separate because there is a temperature difference between the fluids at at least one end face of the matrix. Furthermore where the heat exchanger is to be employed in a gas turbine engine to exchange heat between hot gases discharged from a turbine and compressed air delivered by a compressor of the engine, there is also a pressure differential between the air and the gas and furthermore leakage of the compressed air to the exhaust gases should be kept to a minimum. The seals are usually resilient and may be internally pressurized to maintain effective contact with the matrix, during the rotation of the matrix relatively to the seals, which are usually stationary, and also to permit relative expansion between the seals and the matrix. Seals used in rotary regenerative heat exchangers of the foregoing kind are often of segmental or D-shape and comprise an arcuate outer portion substantially co-axial with the matrix and a diametral or chord-wise portion co-operating with the arcuate portion to define a closed area or areas of segmental shape. Known seals of this kind either have integral arcuate and transverse portions or separate arcuate and transverse portions. An object of the invention is to provide in a rotary regenerative heat exchanger of the foregoing kind at at least one end of the matrix thereof a seal comprising arcuate and transverse portions arranged to permit effective sealing to be maintained and to be substantially stress-free when hot despite relative expansion between the arcuate and transverse seal portions.